Tube coupling

ABSTRACT

A tube coupling for coupling tubes capable of carrying corrosive fluids, the tube coupling employing an outer body of relatively rigid, high strength material, an inner tubular member of a resiliently deformable, generally inert, corrosion resistant material such as a fluorocarbon resin received within the outer body and having a bore for receiving a tube therein, an annulus of elastomeric material having a first portion placed around the inner tubular member adjacent an end thereof and a second portion extending beyond the end of the inner tubular member, the annulus retaining the inner tubular member within the outer body against inadvertent removal therefrom, a nut threaded onto the outer body and means coupling the nut and the annulus such that upon threading the nut along the outer body the coupling means will axially contract the annulus to radially contract the inside diameter of the first portion of the annulus and thereby deform the inner tubular member radially inwardly to grip the tube therein and establish a seal between the inner tubular member and the tube therein and to radially contract the inside diameter of the second portion of the annulus and thereby grip the tube therein in response to axial movement of the threaded member.

United States Patent [72] Inventor Lloyd K. Dutton West Paterson, NJ.[21] Appl. No. 804,581 [22] Filed Mar. 5, 1969 [45] Patented May 18,1971 [73] Assignee Mooney Brothers Corporation Little Falls, NJ.

[54] TUBE COUPLING 4 Claims, 4 Drawing Figs. [52] US. Cl. 285/55,285/343, 285/348, 285/369 [51] lnt.Cl F161 9/14 [50] Field of Search285/55, 343, 364, 351, 423, 337, 348, 342

[56] References Cited UNITED STATES PATENTS 834,618 10/1906 Herrick285/337 3,188,122 6/1965 Smith 285/369X 3,233,920 2/ 1966 Ammann285/423X 3,432,187 3/1969 Mooney et al. 285/55 FOREIGN PATENTS 475,6444/1929 Germany 285/342 Primary Examiner-Dave W. Arola AttorneySamuelson& Jacob ABSTRACT: A tube coupling for coupling tubes capable of carryingcorrosive fluids, the tube coupling employing an outer body ofrelatively rigid, high strength material, an inner tubular member of aresiliently deformable, generally inert, corrosion resistant materialsuchas a fluorocarbon resin received within the outer body and having abore for receiving a tube therein, an annulus of elastomeric materialhaving a first portion placed around the inner tubular member adjacentan end thereof and a second portion extending beyond the end of theinner tubular member, the annulus retaining the inner tubular memberwithin the outer body against inadvertent removal therefrom, a nutthreaded onto the outer body and means coupling the nut and the annulussuch that upon threading the nut along the outer body the coupling meanswill axially contract the annulus to radially contract the insidediameter of the first portion of the annulus and thereby deform theinner tubular member radially inwardly to grip the tube therein andestablish a seal between the inner tubular member and the tube thereinand to radially contract the inside diameter of the second portion ofthe annulus and thereby grip the tube therein in response to axialmovement of the threaded member.

TUBE COUPLING The present invention relates generally to tube couplingsand pertains more specifically to tube couplings for coupling tubescapable of carrying corrosive fluids and assuring that the corrosivefluid is isolated from those structural components of the coupling whichmay be susceptible tocorrosion. The term corrosive fluids is meant toencompass all fluids which should be isolated from those structuralcomponents of the coupling which are susceptible to some unfavorablereaction with the fluid conducted through the coupling, including thosefluids which might themselves be contaminated or otherwise degraded bycontact with the structural components, such as pure or ultra-purefluids which must be maintained at a high level of purity.

In many laboratory and manufacturing plant installations, variousexperiments and processes are carried out which require that a varietyof corrosive fluids be conducted through networks of tubes. The tubesare usually fabricated of generally inert, corrosion resistantmaterials. Many of these materials, such as glass and ceramics, arefrangible and any coupling which is employed to join the tubes at thevarious junctures in these networks should exert a firm, but gentle gripupon the joined tubes so as to maintain the connection rigid withoutplacing undue stress upon the tubes themselves. At the same time, thejoints should be sealed against leakage. of the corrosive fluid from theconnection and against the exposure of corrodible component parts of thecoupling to the corrosive fluid.

It is therefore an important object of the invention to provide a tubecoupling which affords a rigidconnection between tubes of corrosionresistant material and which confines corrosive fluids passing throughthe connection to contact with only generally inert, corrosion resistantcomponent parts of the coupling.

Another object of the invention is to provide a tube coupling combiningthe relatively rigid, high strength characteristics of metalliccomponents such as steel or aluminum with the resiliently deformable andcorrosion resistant characteristics of certain generally inert syntheticresin materials such as fluorocarbon resins.

A further object of the invention is to provide a tube coupling in whichthe corrosion resistant characteristics of synthetic resin materialssuch as fluorocarbon resins are used to best advantage while thegripping characteristics of elastomeric materials are employed for morepositively securing together coupled tubes.

A still further object of the invention is to provide a tube couplinghaving a simplified construction with a minimum number of componentparts, each having a readily fabricated configuration.

The above objects, as well as further objects and ad'- vantages, areattained in the invention which can be described briefly as a tubecoupling for coupling tubes capable of carrying corrosive fluids, thetube coupling comprising an outer body of relatively rigid, highstrength material including an axial bore having an axial length betweenopposite ends, the outer body including a shoulder adjacent at least oneof the opposite ends of the bore, an inner tubular member of aresiliently deformable, generally inert, corrosion resistant materialsuch as a fluorocarbon resin, received. within the bore of the outerbody and having an inside diameter complementary to a tube to bereceived therein and a relatively larger outside diameter, the innermember having an axial. length between opposite ends greater than thelength of the bore, means adjacent each of the opposite ends of the borefor retaining the inner tubular member within the bore of the outer bodyagainst inadvertent removal therefrom, the means including an annulus ofelastomeric material having afirst portion located around the innertubular member adjacent one end thereof and abutting the shoulder in thebore, and a second portion extending axially away from the shoulderbeyond the one end of the inner tubular member, the first portion havingan inside diameter complementary to and overlapping the inner tubularmember and the second portion having an inside diameter complementary toand overlapping a tube to be received therein, a threaded memberthreaded onto the outer body for axial movement relative thereto, andmeans coupling the threaded member the annulus for engaging and axiallycontracting the annulus to radially contract the inside diameter of thefirst portion thereof and thereby deform the first portion withconcomitant deformation 8 the inner tubular member radially inwardly togrip the tube therein and establish a seal between the inner tubularmember and the tube, and to radially contract the inside diameter of thesecond portion thereof and thereby deform the second portion radiallyinwardly to grip the tube therein in response to axial movement of thethreaded member the inside diameter of the second portion of the annulusbeing smaller than the inside diameter of the first portion of theannulus, the annulus including a step between the inside diameters ofthe first and second portions thereof, the step abutting the one end ofthe inner tubular member, the first portion having a generallycylindrical outer surface and the second portion having an outer surfacewhich tapers axially from a larger outside diameter at the generallycylindrical surface to a smaller outside diameter spaced axially awayfrom the one end of the inner tubular member.

The invention will be more fully understood and still further objectsand advantages will become apparent in the following detaileddescription of a preferred embodiment of the invention illustrated inthe accompanying drawing, in which:

FIG. l is a longitudinal cross-sectional view of a junction betweentubes and illustrating a tube coupling constructed in accordance withthe invention;

FIG. 2 is an end view of the junction of FIG. 1;

FIG. 3 is an enlarged fragmentary view of a portion of the junction ofFIG. I; and

FIG. 4 is an enlarged fragmentary view similar to FIG. 3, but with thecomponent parts of the tube coupling in another position.

Referring now to the drawing, and especially to FIGS. 1 and 2, a tubecoupling constructed in accordance with the invention is shown generallyat 10 and is seen receiving the confronting ends of tubes 12 and 14 tobe joined in a connection. The tubes 12 and 14 are fabricated of acorrosion resistant material such as glass.

Coupling 10 has an outer body 20 including a bore 22 extending axiallybetween shoulders 24 at opposite ends of the bore 22. An inner tubularmember shown in the form of a sleeve 26 of resiliently deformable,corrosion resistant material is received within the bore 22 and extendsaxially beyond the shoulders 24 of the bore. The inside diameter ofsleeve 26 is complementary to the outside diameter of the tubes 12 and14 so that the tubes are readily inserted into the sleeve and advancedwithin the sleeve until the end of each tube abuts a centering stopshoulder 28 provided by an annular rib 30 formed integral with the wallof sleeve 26 and having an inside diameter smaller than the insidediameter of the sleeve and the corresponding outside diameter of eachtube.

In order to retain the sleeve 26 in place within the outer body 20against inadvertent removal from the bore 22, an annulus 32 ofelastomeric material is slipped over each end of the sleeve 26. Eachannulus is received within a recess 34 in the outer body 20 and isbrought into abutment with a shoulder 24.

Each annulus 32 has. a first portion 36 located around the sleeve 26adjacent oneend thereof and abutting a shoulder 24, and a second portion38 extending axially away from the shoulder 24 and beyondthecorresponding end of the sleeve 26. The first portion 36 has aninside diameter which is complementary to the outside diameter of thesleeve 26 and overlaps the sleeve. The second. portion 38 has an insidediameter As best seen in FIGS. 1 and 3, the inside diameter of thesecond portion 38 is smaller than the inside diameter of the firstportion 36 of the annulus 32 and a step 40 is established a between thedifferent inside diameters of the inner surface of the annulus 32. Thestep 40 abuts the corresponding end of the sleeve 26.

The sleeve 26 is preferably retained in place within the bore 22 of body20 by providing the inside diameter of the first portion 36 of annulus32 and the outside diameter of sleeve 26 with relative normal dimensionswhich require that the annulus be diluted in order to bring the firstportion into the overlapping assembled position shown. Such dilationestablishes a frictional force with which the annulus grips the sleeveso that the two annuli 32 retain the sleeve 26 within the bore 22against inadvertent removal therefrom.

The abutting relationship between the steps 40 and the correspondingends of the sleeve 26 also serves to retain the sleeve in place withinthe bore 22 of body 20. Thus, retention of the sleeve 26 may beaccomplished either through the gripping action of the first portion 36of each annulus upon the sleeve as set forth above, or by abutment ofthe steps 40 with the ends of the sleeve, or by a combination of bothmeasures.

The tubes are clamped within the coupling by threaded members shown inthe form of clamping nuts 42 which are threaded onto threaded portions44 of the outer body 20 for axial movement relative to the outer body.Means are provided for coupling each nut 42 with a corresponding annulus32 and are shown in the form of a flange portion 46 on each nut engaginga gland 48 which is located between each annulus 32 and a correspondingflange portion 46 for axial sliding movement relative to the outer body20. The nuts 42 are ordinarily positioned to allow insertion of tubes 12and 14 into sleeve 26 and annuli 32 as seen in FIG. 3. Upon the advance'ment of a nut 42 along the outer body, to the left as seen in FIG. 4,the flange 46 of the nut will engage a corresponding gland 48 and thegland will exert an axial pressure upon the annulus 32. Since theannulus is confined within the recess 34 and cannot expand eitheraxially or radially outwardly, the axial pressure of the gland willcontract the annulus axially and will contract the inside diameter ofthe first portion 36 of the annulus radially inwardly to deform thesleeve 26 against the tube 12 at 50. The deformation of sleeve 26establishes a firm but gentle clamping force which will secure tube 12within the sleeve 26 and within the coupling 10. At the same time, thedeformation of sleeve 26 establishes a seal between the sleeve and thetube so that any corrosive fluid being conducted through the tubes isconfined within the tubes and within the sleeve 26.

Such axial contraction of the annulus will also radially contract theinside diameter of the second portion 38 of the annulus such that thesecond portion 38 will bear against the corresponding tube 12 and exerta further gripping force upon the tube to more firmly secure the tube inplace within the coupling. The seal established by the engagement of thesleeve 26 against the tube 12 (or 14) will preclude corrosive fluidswhich flow through the coupled tubes from contacting the an nuli.

In order to enhance the tube-gripping action of the second portion 38 ofeach annulus while enabling the first portion 36 to deform the sleeve 26as described above, the first portion is provided with a cylindricalouter surface 52 (see FIG. 3) and the second portion 38 is provided witha frustoconical outer surface 54 which tapers axially from the largeroutside diameter of the first portion 36 to the smaller outside diameterat the outer end 56 of the annulus. Each gland 48 is provided with acomplementary frustoconical inner surface 58 which engages and bearsagainst the corresponding frustoconical outer surface 54 to axiallycontract each annulus and radially contract the inside diameters thereofin response to axial movement of each nut 42.

It is important that the joint thus established between the tubes 12 and14 be relatively rigid as well as well sealed. Thus,

the outer body 20 is constructed of a relatively rigid, high strengthmaterial, preferably a metal such as steel or aluminum. The outer body20 and the sleeve 26 are long enough to receive a sufficient length ofthe tubes 12 and 14 to assure a relatively rigid connection between thetubes. The centering stop shoulders 28 provided by annular rib 30assures that both tubes 12 and 14 will be inserted for such a sufficientlength.

The outer body 20, as well as nuts 42, is provided with a wrenchingconfiguration at 60 so as to enable the outer body 20, as well as thenuts 42, to be easily gripped for controlled advance of the nuts and acontrolled buildup of the forces acting to grip the tubes. Such controlis advantageous in view of the frangible nature of most of the corrosionresistant materials employed for the tubes 12 and 14. Additionally, thenature of the material of the outer body 20 permits ready modificationof the outer body 20 to conform to the requirements of a particularinstallation. For example, one or more tapped holes, such as tappedholes 62, may be provided in the outer body for receiving anchor rods(not shown) which will hang or otherwise mount the coupling within thesystem in which the coupling 10 is installed.

Each annulus 32 is preferably fabricated of an elastomeric material suchas rubber or Neoprene and is confined to recess 34, which communicateswith sleeve 26, in order to attain controlled contraction of the annuliand the sleeve without interfering with the advancement of the nuts 42.

The sleeve 26 is preferably fabricated of a synthetic resin materialsuch as a fluorocarbon resin. A fluorocarbon resin such aspolytetrafluoroethylene has been found to provide adequate corrosionresistant characteristics as well as being resiliently deformable to theextent required. Because the sleeve 26 is a simple cylindrical shape,the sleeve is easily fabricated and readily replaced.

lt is to be understood that the above detailed description of apreferred embodiment of the invention is provided by way of exampleonly. Various details of design and construction may be modified withoutdeparting from the true spirit and scope of the invention.

lclaim:

1. A tube coupling for coupling tubes capable of carrying corrosivefluids, said tube coupling comprising:

an outer body of relatively rigid, high strength material including anaxial bore having an axial length between opposite ends, said outer bodyincluding a shoulder adjacent at least one of said opposite ends of thebore;

an inner tubular member of resiliently deformable,

generally inert, corrosion resistant material such as a fluorocarbonresin received within the bore of the outer body and having an insidediameter complementary to a tube to be received therein and a relativelylarger outside diameter, said inner tubular member having an axiallength between opposite ends greater than the length of said bore;

means adjacent each of said opposite ends of the bore for retaining theinner tubular member within the bore of the outer body againstinadvertent removal therefrom, said means including an annulus ofelastomeric material having a first portion located around the innertubular member adjacent one end thereof and abutting the shoulder in thebore and a second portion extending axially away from the shoulderbeyond said one end of the inner tubular member, said first portionhaving an inside diameter complementary to and overlapping said innertubular member and said second portion having an inside diametercomplementary to and overlapping a tube to be received therein;

a threaded member threaded onto the outer body for axial movementrelative thereto;

means coupling the threaded member and the annulus for engaging andaxially contracting the annulus to radially contract the inside diameterof the first portion thereof and thereby deform the first portion withconcomitant deformation of the inner tubular member radially inwardly togrip the tube therein and establish a seal between the inner tubularmember and the tube, and to radially contract the inside diameter of thesecond portion thereof and thereby deform the second portion radiallyinwardly to grip the tube therein in response to axial movement of thethreaded member;

the inside diameter of the second portion of the annulus being smallerthan the inside diameter of the first portion of the annulus, theannulus including a step between the inside diameters of the first andsecond portions thereof, said step abutting said one end of the innertubular member;

said first portion having a generally cylindrical-outer surface; and

said second portion having an outer surface which tapers axially from alarger outside diameter at said generally cylindrical surface to asmaller outside diameter spaced axially away from said one end of theinner tubular member.

2. A tube coupling for coupling tubes capable of carrying corrosivefluids, said tube coupling comprising:

an outer body of relatively rigid, high strength material including anaxial bore having an axial length between opposite ends, said outer bodyincluding a shoulder adjacent at least one of said opposite ends of thebore;

an inner tubular member of resiliently deformable, generally inert,corrosion resistant material such as a fluorocarbon resin receivedwithin the bore of the outer body and having an inside diametercomplementary to a tube to be received therein and a relatively largeroutside diameter, said inner tubular member having an axial lengthbetween opposite ends greater than the length of said bore;

means adjacent each of said opposite ends of the bore for retaining theinner tubular member within the bore of the outer body againstinadvertent removal therefrom, said means including an annulus ofelastomeric material having a first portion located around the innertubular member adjacent one end thereof and abutting the shoulder in thebore and a second portion extending axially away from the shoulderbeyond said one end of the inner tubular member, said first portionhaving an inside diameter complementary to and overlapping said innertubular member and said second portion having an inside diametercomplementary to and overlapping a tube to be received therein;

a threaded member threaded onto the outer body for axial movementrelative thereto;

means coupling the threaded member and the annulus for engaging andaxially contracting the annulus to radially contract the inside diameterof the first portion thereof and thereby deform the first portion withconcomitant deformation of the inner tubular member radially inwardly togrip the tube therein and establish a seal between the inner tubularmember and the tube, and to radially contract the inside diameter of thesecond portion thereof and thereby deform the second portion radiallyinwardly to grip the tube therein in response to axial movement of thethreaded member;

said first portion of the annulus having a generally cylindrical outersurface;

said second portion of the annulus having a frustoconical outer surface;and

said means coupling the threaded member and the annulus including afrustoconical inner surface complementary to said frustoconical outersurface of the second portion and each of said 0 posite ends of thebore; an inner tubu generally inert, corrosion resistant material suchas a fluorocarbon resin received within the bore of the outer body andhaving an inside diameter complementary to a tube to be received thereinand a relatively larger outside diameter, said inner tubular memberhaving an axial length between opposite ends greater than the length ofsaid bore and projecting axially outwardly beyond each shoulder of theouter body;

means adjacent each of said opposite ends of the bore for retaining theinner tubular member within the bore of the outer body againstinadvertent removal therefrom, said means including an annulus ofelastomeric material adjacent each end of the inner tubular member, eachannulus having a first portion located around the inner tubular memberadjacent an end thereof and abutting a corresponding shoulder in thebore and a second portion extending axially away from the correspondingshoulder beyond said end of the inner tubular member, said first portionhaving an inside diameter complementary to and overlapping said innertubular member and said second portion having an inside diameter smallerthan the inside diameter of the first portion and complementary to andoverlapping a tube to be received therein;

a threaded member threaded onto each end of the outer body for axialmovement relative thereto;

means coupling each threaded member with an annulus for engaging andaxially contracting the annulus to radially contract the inside diameterof the first portion thereof and thereby deform the first portion withconcomitant' deformation of the inner tubular member radially inwardlyto grip the tube therein and establish a seal between the inner tubularmember and the tube, and to radially contract the inside diameter of thesecond portion thereof and thereby deform the second portion radiallyinwardly to grip the tube therein in response to axial movement of thecorresponding threaded member;

each annulus including a step between the inside diameters of the firstand second portions thereof, each said step abutting a corresponding endof the inner tubular member;

each first portion having a generally cylindrical outer surface;

each second portion having a frustoconical outer surface;

and

said means coupling each threaded member and each annulus including afrustoconical inner surface complementary to said frustoconical outersurface of a corresponding second portion and engageable therewith.

4. The tube coupling of claim 3 wherein:

each threaded member is a nut; and

the means coupling each threaded member and a corresponding annulusinclude a flange integral with the nut and an axially slideable annulargland located between each annulus and a corresponding flange, eachgland including said frustoconical inner surface and each flangeengaging a corresponding gland to urge the gland against a correspondingannulus in response to movement of the corresponding nut along the outerbody.

ar member of resiliently deformable, v

1. A tube coupling for coupling tubes capable of carrying corrosivefluids, said tube coupling comprising: an outer body of relativelyrigid, high strength material including an axial bore having an axiallength between opposite ends, said outer body including a shoulderadjacent at least one of said opposite ends of the bore; an innertubular member of resiliently deformable, generally inert, corrosionresistant material such as a fluorocarbon resin received within the boreof the outer body and having an inside diameter complementary to a tubeto be received therein and a relatively larger outside diameter, saidinner tubular member having an axial length between opposite endsgreater than the length of said bore; means adjacent each of saidopposite ends of the bore for retaining the inner tubular member withinthe bore of the outer body against inadvertent removal therefrom, saidmeans including an annulus of elastomeric material having a firstportion located around the inner tubular member adjacent one end thereofand abutting the shoulder in the bore and a second portion extendingaxially away from the shoulder beyond said one end of the inner tubularmember, said first portion having an inside diameter complementary toand overlapping said inner tubular member and said second portion havingan inside diameter complementary to and overlapping a tube to bereceived therein; a threaded member threaded onto the outer body foraxial movement relative thereto; means coupling the threaded member andthe annulus for engaging and axially contracting the annulus to radiallycontract the inside diameter of the first portion thereof and therebydeform the first portion with concomitant deformation of the innertubular member radially inwardly to grip the tube therein and establisha seal between the inner tubular member and the tube, and to radiallycontract the inside diameter of the second portion thereof and therebydeform the second portion radially inwardly to grip the tube therein inresponse to axial movement of the threaded member; the inside diameterof the second portion of the annulus being smaller than the insidediameter of the first portion of the annulus, the annulus including astep between the inside diameters of the first and second portionsthereof, said step abutting said one end of the inner tubular member;said first portion having a generally cylindrical outer surface; andsaid second portion having an outer surface which tapers axially from alarger outside diameter at said generally cylindrical surface to asmaller outside diameter spaced axially away from said one end of theinner tubular member.
 2. A tube coupling for coupling tubes capable ofcarrying corrosive fluids, said tube coupling comprising: an outer bodyof relatively rigid, high strength material including an axial borehaving an axial length between opposite ends, said outer body includinga shoulder adjacent at least one of said opposite ends of the bore; aninner tubular member of resiliently deformable, generally inert,corrosion resistant material such as a fluorocarbon resin receivedwithin the bore of the outer body and having an inside diametercomplementary to a tube to be received therein and a relatively largeroutside diameter, said inner tubular member having an axial lengthbetween opposite ends greater than the length of said bore; meansadjacent each of said opposite ends of the bore for retaining the innertubular member within the bore of the outer body against inadvertentremoval therefrom, said means including an annulus of elastomericmaterial having a first portion located around the inner tubular mEmberadjacent one end thereof and abutting the shoulder in the bore and asecond portion extending axially away from the shoulder beyond said oneend of the inner tubular member, said first portion having an insidediameter complementary to and overlapping said inner tubular member andsaid second portion having an inside diameter complementary to andoverlapping a tube to be received therein; a threaded member threadedonto the outer body for axial movement relative thereto; means couplingthe threaded member and the annulus for engaging and axially contractingthe annulus to radially contract the inside diameter of the firstportion thereof and thereby deform the first portion with concomitantdeformation of the inner tubular member radially inwardly to grip thetube therein and establish a seal between the inner tubular member andthe tube, and to radially contract the inside diameter of the secondportion thereof and thereby deform the second portion radially inwardlyto grip the tube therein in response to axial movement of the threadedmember; said first portion of the annulus having a generally cylindricalouter surface; said second portion of the annulus having a frustoconicalouter surface; and said means coupling the threaded member and theannulus including a frustoconical inner surface complementary to saidfrustoconical outer surface of the second portion and engageabletherewith.
 3. A tube coupling for coupling tubes capable of carryingcorrosive fluids, said tube coupling comprising: an outer body ofrelatively rigid, high strength material including an axial bore havingan axial length between opposite ends, said outer body including ashoulder adjacent each of said opposite ends of the bore; an innertubular member of resiliently deformable, generally inert, corrosionresistant material such as a fluorocarbon resin received within the boreof the outer body and having an inside diameter complementary to a tubeto be received therein and a relatively larger outside diameter, saidinner tubular member having an axial length between opposite endsgreater than the length of said bore and projecting axially outwardlybeyond each shoulder of the outer body; means adjacent each of saidopposite ends of the bore for retaining the inner tubular member withinthe bore of the outer body against inadvertent removal therefrom, saidmeans including an annulus of elastomeric material adjacent each end ofthe inner tubular member, each annulus having a first portion locatedaround the inner tubular member adjacent an end thereof and abutting acorresponding shoulder in the bore and a second portion extendingaxially away from the corresponding shoulder beyond said end of theinner tubular member, said first portion having an inside diametercomplementary to and overlapping said inner tubular member and saidsecond portion having an inside diameter smaller than the insidediameter of the first portion and complementary to and overlapping atube to be received therein; a threaded member threaded onto each end ofthe outer body for axial movement relative thereto; means coupling eachthreaded member with an annulus for engaging and axially contracting theannulus to radially contract the inside diameter of the first portionthereof and thereby deform the first portion with concomitantdeformation of the inner tubular member radially inwardly to grip thetube therein and establish a seal between the inner tubular member andthe tube, and to radially contract the inside diameter of the secondportion thereof and thereby deform the second portion radially inwardlyto grip the tube therein in response to axial movement of thecorresponding threaded member; each annulus including a step between theinside diameters of the first and second portions thereof, each saidstep abutting a corresponding end of the inner tubular member; eachfirst portion having a generally cylindrical outer surface; each secondportion having a Frustoconical outer surface; and said means couplingeach threaded member and each annulus including a frustoconical innersurface complementary to said frustoconical outer surface of acorresponding second portion and engageable therewith.
 4. The tubecoupling of claim 3 wherein: each threaded member is a nut; and themeans coupling each threaded member and a corresponding annulus includea flange integral with the nut and an axially slideable annular glandlocated between each annulus and a corresponding flange, each glandincluding said frustoconical inner surface and each flange engaging acorresponding gland to urge the gland against a corresponding annulus inresponse to movement of the corresponding nut along the outer body.